[Linux-cluster] Re: Does GFS support MD multi-device in a two node cluster?

Kevin Anderson kanderso at redhat.com
Wed Jul 12 18:53:27 UTC 2006

On Thu, 2006-07-13 at 02:34 +0800, jOe wrote:
> On 7/11/06, jOe <smartjoe at gmail.com> wrote:
>         Hello All,
>         We want to confirm that GFS support SCSI based MD multi-device
>         configuration?
>         Server: HP dl380g4 x 2, each has 4-port additional array
>         adapter installed
>         Storage: HP MSA500g2, SCSI array disk system, has 4-port
>         option installed, support 4 SCSI cable connect to this
>         system.(4 individual physical server or two server with dual
>         SCSI path.) 
>         OS: RHEL4U3

This storage won't work well with GFS.  GFS requires you are able to
have concurrent access to the storage devices from more than one machine
at the same time.  The SCSI bus will lock out other accesses for periods
of time when a node is reading or writing to the file system.  The
storage is fine in a failover configuration, but GFS will pound it and
it will not survive.

>         We've already deployed RHCS on it (without GFS) and use
>         linux's MD multi-device for SCSI multi-path. (merge two lun
>         path from the disk array to single failover path.  /dev/sda
>         +/dev/sdb ->/dev/md0) 
>         Question: Can we deploy GFS on such hardware configuration and
>         is it possible to create GFS on MD multi-device ? Any pros and
>         cons?

It is possible to create GFS on an MD device as long as you are only
using it for multipath.  The preferred solution is to use device mapper
multipathing rather than md in these configurations.

The bigger problem is the type of storage and connectivity you are
using.  You will not be happy with the performance you get from the
storage when using GFS.



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